The invention relates to a liquid electrolyte or electrolytic battery, which is preferably used in moving vehicles, such as e.g. cars, boats or aircraft.
The efforts more particularly made by the vehicle industry for lightweight construction also concerns the economizing of battery weight. However, there is at the same time an increasing demand for a higher battery power, because in addition to conventional energy for starting the vehicle, energy is also required for additional units such as electric window regulators, actuators or servomotors for adjusting seats and for the electric heating of the seats. It is desirable to keep the battery power at a constant high level over the entire battery life.
The prior art discloses various measures for increasing the power of a conventional lead acid battery. The term power is here understood to mean the capacity of the battery and the current output and consumption capability of the battery.
A particular problem arising with lead acid batteries is the optimum complete use of the electrode surface. FIGS. 1 to 3 are intended to illustrate the problem known from the prior art. FIG. 1 is a sectional representation of a car battery 1 along its electrodes 2, which have a grid form in the present construction. The level of the battery acid 3 is designated 3a. Research has revealed that the chemical characteristics of the battery acid differ significantly in the areas designated a, b and c. Thus, in area a the acid concentration is too high, which leads to corrosion and ultimately to the disintegration of the plates. In area c the acid concentration is too low, i.e. the electrolytic characteristics necessary for the operation of the battery do not exist.
Only in the central area b does the acid have the optimum stoichiometric ratio. Thus, the existing electrode surface is not utilized in an optimum manner due to the inadequate acid characteristics in areas a and c. It is clear to the expert that the areas are not sharply defined in the manner shown.
In order to also improve the stoichiometric ratio in areas a and c, it is known from the prior art to circulate the battery acid, i.e. the electrolyte, in order to obtain a better intermixing. This simultaneously prevents the formation of deposits, which impair the function and life of the battery.
DE-U1 9114909 discloses a storage battery, in which by means of the introduction of gas from a pressurized gas source, an electrolyte circulation is brought about. Due to their complicated construction such devices are unsuitable for vehicle batteries, particularly as additionally a pressurized gas source is needed.
The prior art also discloses electrolyte intermixing devices, which can be called hydrostatic pumps. FIGS. 29a, 29b and 29c show the basic operation of such a device. FIG. 29a is a sectional representation of an electrolyte- filled battery box, which has a double bent plate 21, a portion of the angle projecting beyond the electrolyte surface. To facilitate understanding the electrode plates are not shown. If the battery box installed in a vehicle moves at a uniform speed v, i.e. the vehicle neither accelerates nor decelerates, the electrolyte surface is flat and horizontal. FIG. 29b shows that during a braking process, due to the mass moment of inertia, the electrolyte builds up to a wave in the travel direction and the electrolyte splashes over the upper portion of the plate edge. As now the liquid level between the angle and the casing wall is higher, according to FIG. 29c the electrolyte flows downwards until the two levels have evened out. The arrows show the electrolyte flow direction.
This principle is inter alia described in U.S. Pat. No. 4,963,44, U.S. Pat. No. 5,096,787 and U.S. Pat. No. 5,032,476. However, the inventors of the present invention have found that with the devices known from this prior art it is not possible to achieve an optimum electrolyte intermixing.
Therefore the problem of the invention is the provision of a liquid electrolyte battery for vehicles, in which the necessary higher battery capacity and life are to be achieved mainly through an improved electrolyte intermixing.
One aspect of the invention involves providing a plate element that extends across upper edges of the electrodes to restrain an upward flow of surging electrolyte and thereby intensify an upward float of electrolyte through a vertical flow channel. The advantage of the invention is that the liquid electrolyte circulating device brings about a high degree of intermixing and consequently the battery capacity is significantly increased and simultaneously the battery life is lengthened. The liquid electrolyte circulating device has no free moving parts, whose movement could be impeded by electrolyte deposits. Therefore this device operates very reliably. In addition, the liquid electrolyte circulating device is very inexpensively manufacturable and can be readily integrated into the battery manufacturing technology. Unlike in the case of the prior art, hydrostatic electrolyte pumps, this device pumps the electrolyte from bottom to top. The inventors have proved that in this way intermixing can be significantly improved. Obviously it is advantage for intermixing purposes if the thicker bottom acid is forced upwards and runs out over the horizontal part of the intermixing device, in order to mix with the thinner surface acid.
In the case of a liquid electrolyte battery further developed, parallel to the vertical edges is provided a second, plate-like element, in order to form a flow channel. Thus, the flow conditions can be set in a more clearly defined manner and optimized.
In a liquid electrolyte battery further developed, the first plate-like element and the second plate-like element are constructed in one piece as angles, so that in certain cases an easier assembly is possible.
In a liquid electrolyte battery further developed, in the vicinity of the upper edge of the first plate-like element is provided a first return flow preventer for preventing the return flow of a first electrolyte wave, which improves intermixing.
In a liquid electrolyte battery further developed, the return flow preventer is constructed as a web-like material extension of the first plate-like element, which is particularly cost-effective.
In a liquid electrolyte battery further developed, the return flow preventer is constructed as a flap valve, which particularly effectively prevents a return flow.
In a liquid electrolyte battery further developed, the liquid electrolyte circulating device is placed on both casing sides, which brings about an improved intermixing.
Another advantage of the invention is that through heat convection there is even a thorough mixing or intermixing when the battery is only slightly moved or not moved at all, the heating elements being so positioned that a powerful electrolyte flow can be produced.
Use is made of panel heaters, which are placed on or in the casing wall. If the battery is constructed from two cell groups, which are interconnected by a common partition, the heating means can be placed on said partition located in the center of the battery. Virtually no heat losses occur in this embodiment.
For the protection of the electrode plates a heat shield is provided, so that the electrolyte heated by the heating means does not pass directly to the electrode plates. In a particularly preferred embodiment, part of the mechanical circulating device is simultaneously used as a heat shield, so that both a mechanically caused and a thermally caused circulation of the electrolyte takes place.
An advantage of the invention is that in the same way as for producing a convection by means of heating elements, an intermixing still occurs if the battery moves only slightly or is stationary.
The cooling involves the same effect, but it is brought about with different means. Thus, there can be a combination thereof with the mechanical circulating device.